At present, joint damage, such as cartilage damage, is treated by replacing the joint with an artificial joint. However, serious complications are caused by the replacement of artificial joints, in particular a high occurrence rate of loosening problems resulting in breakage of the bones around the artificial joint.
In particular, the invasive character of the fixation of the prostheses such as anchoring of the prosthesis with screws and pins results in numerous side-effects such as risk of infection, loosening as mentioned above, damage on excising bone due to interruption of blood supply and necrosis.
A device for replacement within a joint should preferably enable the normal function and movements of the joint. Weight-bearing joints, in which movement in more than one direction takes place, are normally rather difficult to replace.
A prosthetic device should enable the normal movement of the joint. During walking, the normal movement of for example the hip joint corresponds to about 370-410 flexion/extension, 20-140 adduction/abduction and a rotation of about 20-160. During movement from standing to sitting position a flexion of hip joint corresponds to a movement from 0 to 90 degrees. When studying the movement of femoral caput to the acetabulum the latter movement includes a rotation of 90 degrees.
So far, no satisfactory device for placement within a joint has been achieved in the prior art.